Blower construction



June 1957 E. \NAXENBERGER 3,3

BLOWER CONSTRUCTION Filed Aug .10, 1964 IFIG.|

INVENTOR 131:? ERICH WAXENBERGER ATTORNEYS United States Patent 3,326,297 BLOWER CONSTRUCTION Erich Waxenherger, Neuhausen auf den Filrlern, Germany, assignor to Daimier-Benz Aktiengesellschaft, Stuttgart-Unterturkheim, Germany Filed Aug. 10, 1%4, Ser. No. 388,439 21 Claims. (Cl. 170-16053) The present invention relates to an adjusting mechanism for blades, or vanes pivotally arranged about pins in the hub portion of radiator fans or cooling blowers for internal combustion engines installed into motor vehicles, in which the blades are held against a fixed abutment by the prestress of a spring in the sense of a maximum pitch angle until air pressure acting during operation on the blades constructed asymmetrically in relation to the longitudinal axes thereof automatically readjusts the same to a smaller pitch, that is, to a lesser delivery or smaller output, and in which cranks are provided at the radially inwardly disposed ends of the blade pins whose crankpins engage in cam-tracks that are arranged in a sliding member axially guided within the blower hub portion.

With cooling blowers for internal combustion engines installed into motor vehicles or with fans that rotate behind the liquid radiator of the internal combustion engine, it is known in the prior art to control the sliding member, axially guided within the blower hub, by means of a thermostat acted upon by the warmed-up cooling air stream in order to correspondingly adjust the pitch angle of the blades in dependence on the temperature of the warmed-up cooling air. The thermostat of such prior art construction has to take over the actuation of the sliding piece in both directions, which, however, is disadvantageous in so far as thermostats normally are not in a position to exert larger pulling or drawing forces.

With another adjusting mechanism known in the prior art, the blades pivotally supported on the blower drive shaft are provided with adjusting levers which carry at the free ends thereof rollers that rest against a plate supported displaceably in the axial direction on the forward shaft end and subjected to the presstress of a spring. During standstill of the blower or fan, the blades of such prior art construction are held by the spring force in the position of largest pitch angle. With increasing rotational speed, the air pressure acting on the blades, constructed asymmetrically in relation to the longitudinal axes thereof, automatically readjusts the same to an ever smaller pi-tch against the resistance of the spring in order to obtain an approximately constant output or delivery over the entire rotational speed range. The disadvantage of this known arrangement consists in that exclusively the factor rotational speed enters controllingly into the operation.

The present invention is predicated on the task to create a cooling blower or fan whose blades are adjusted in dependence on both the aerodynamic forces as well as the air temperature whereby the arrangement is made in a space-saving manner.

The underlying problems are solved in accordance with the present invention in that the spring producing the prestress. on the one hand, en ages directly with the sliding piece guided within the blower hub and seeks to hold the same against an abutment fixed to the hub, and on the other, is supported against a thermostat that increases or decreases the prestress of the spring and is axially adjustably guided in the blower hub or within a part fixed to the hub and is acted upon by the cooling air.

It is further proposed as an additional feature of the present invention to construct the sliding piece as a hollow body open toward the front against the direction of air flow and provided with a bottom, within which the thermostat is movably arranged in the axial direction. The hollow blower hub is thereby closed at the forward end by a cover provided with cooling air inlet bores within which the adjusting bolt of the thermostat is adjustably guided in a thread, whereby the prestressed spring, on the one hand, is seated against an abutment disk of the thermostat, and, on the other, presses inwardly against the hollow body bottom whose outer surface as a result of the prestressed spring rests against the abutment secured or rigid with the hub.

Accordingly, it is an object of the present invention to provide an adjusting mechanism for pivotally arranged blades in cooling blowers or fans for internal combustion engines which is simple in construction and ofiers a high degree of versatility in the automatic control thereof, yet obviates the aforementioned shortcomings encountered with the prior art constructions.

Another object of the present invention resides in the provision of an adjusting mechanism for automatically ad justing the pitch angle of the blades of a cooling blower or radiator fan which increases the reliability of operation thereof, and assures proper interdependence of several control factors desirable in the control of the pitch angle.

Another object of the present invention resides in the provision of an adjusting mechanism for the blades of radiator fans or cooling blowers in which the automatic adjustment is dependent on both the aerodynamic forces and the air temperature of the cooling air.

Still a further object of the present invention resides in the provision of an automatic adjusting mechanism for the blades of radiator fans or cooling blowers which is compact in construction, easy to assemble and simple to service.

These and other objects, features, and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows for purposes of illustration only one embodiment in accordance with the present invention and wherein FIGURE 1 is a partial side elevational view of a cooling blower in accordance with the present invention, partly in cross section, and

FIGURE 2 is a cross sectional view taken along line IIII of FIGURE 1 with the thermostat and the spring removed for the sake of clarity.

Referring now to the drawing wherein like reference numerals are used throughout the two views to designate like parts, reference numeral 11 designates therein the blower hub portion within which are pivotally supported the pivot pins 12 of the blower blades 16. The pins 12 are provided at the radially inner ends thereof with base plates 13 that, in turn, are provided with crankpins 14 which engage in correspondingly shaped camtracks machined into a slide piece 15. The slide piece 15 is constructed as hollow body which has an external polygonal contour with the number of corners corresponding to the number of blades 16 and which is provided with a bottom 15. A thermostat 17 having an abutment disk 18 is assembled inside of the slide piece 15 and is axially movably supported therein. The hollow blower hub portion 11 is closed in front thereof with a cover 20 within which are provided inflow or inlet bores 20' for the inflow or admission of the cooling air that has passed through the liquid radiator and is heated up as a result thereof; the warmed-up cooling air admitted into the inside of the slide piece 15 through the inlet bores 20' thus acts upon the thermostat 17. A pre stressed spring 2-2 is further provided within the slide piece 15, which spring 22, on the one hand, presses inwardly against the bottom 15 and, on the other, is supported against the disk 18 of the thermostat 17. The thermostat 17 is adjustably guided by means of its threaded bolt or stem 23 within the cover 20 provided with complementary internal threads. Cooling air dscharge bores 24 are provided in the rear part of the slide piece 15 and of the blower hub portion 11.

Operation The operation of the adjusting mechanism in accordance with the present invention is as follows:

During standstill of the blower or fan and up to a predetermined rotational speed in the increasing sense corresponding to the respective prestress of the spring 22, the blades 16 are held by way of the slide piece 15 and the crank pins 14 engaging in correspondingly shaped cam-tracks in the position of maximum output or delivery corresponding to maximum pitch angle, whereby the outer surface of the bottom 15' abuts against an abutment plate 25 rigid with or secured to the hub portion 11. The blades 16 are constructed asymmetrically in relation to the longitudinal axes 26 thereof so that from a predetermined rotational speed in the increasing sense the air pressure continuously decreases the pitch angle of the blades 16 against the resistance of spring 22 in that it compresses the latter.

Due to the ratio of the differently large surfaces disposed on the two sides of the longitudinal blade axes 26 and by reason of the prestress of the spring 22, a cooling air output or delivery can be determined dependent on the prevailing rotational speed over the entire rotational speed range which is matched large limits to the heat economy or cooling air requirements of the internal combustion engine. This condition is considerably improved by the simultaneous inclusion of the control factor cooling air temperature by means of which the thermostat 17 is controlled and which acts on the spring 22 and more or less prestresses the same whereby the output of the blower is additionally increased or decreased over and above the measure determined by the control factor rotational speed. Thus, both influence magnitudes or control factors rotational speed and air temperature are appropriately combined in a single installation whereby the number of structural elements necessary to achieve this combined control feature does not exceed that needed for a simple prior art control installation that considers only one of the two control factors.

While I have shown and described only one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and I therefore do not wish to be limited to the details shown and described herein but intend cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. An adjusting mechanism for automatically adjusting the blades of a blower which are pivotally arranged in the hub portion of the blower, especially for internal combustion engines in motor vehicles, comprising:

blower hub means having fixed abutment means,

a plurality of blade means including pivot pin means rotatably supported within said hub means and crank pin means;

said blade means being of asymmetrical construction with respect to the longitudinal axes thereof,

first means normally holding said blade means in a position of maximum blower output up to a predetermined rotational speed including slide means axially guided within said hub means and provided with cam-track means, follower means at said crankpin means engaging said cam-track means, and prestressed spring means within said slide means and operable in such a manner that the air pressure automatically adjusts the blade means to a lesser output as the rotational speed thereof exceeds said predetermined speed,

and second means for controlling the adjustment of Lil said blade means in dependence on the temperature of the cooling air including thermostat means within said slide means and acted upon by the cooling air, said spring means engaging, on the one hand, directly with said slide means and seeking to hold the same against said fixed abutment means and being supported, on the other, against said thermostat means so that said thermostat means selectively increases or decreases the prestress of said spring means.

2. An adjustment mechanism for automatically adjusting the blades of a blower which are pivotally arranged in the hub portion of the blower, especially for internal combustion engines in motor vehicles, comprising:

blower hub means having fixed abutment means,

a plurality of blade means including pivot pin means rotatably supported within said hub means and crank pin means,

said blade means being of asymmetrical construction with respect to the longitudinal axes thereof,

first means normally holding said blade means in a position of maximum blower output up to a predetermined rotational speed including slide means axially guided within said hub means and provided with cam-track means, follower means at said crankpin means engaging said cam-track means, and prestressed spring means within said slide means and operable in such a manner that the air pressure automatically adjusts the blade means to a lesser output as the rotational speed thereof exceeds said predetermined speed,

and second means for controlling the adjustment of said blade means in dependence on the temperature of the cooling air including thermostat means within said slide means and acted upon by the cooling air, said spring means engaging, on the one hand, directly with said slide means and seeking to hold the same against said fixed abutment means and being supported, on the other against said thermostat means so that said thermostat means selectively increases or 7 the hub portion of the blower, especially for internal com bustion engines in motor vehicles, comprising:

blower hub means having fixed abutment means,

a plurality of blade means including pivot pin means rotatably supported within said hub means and crank pin means,

said blade means being of asymmetrical construction with respect to the longitudinal axes thereof,

first means normally holding said blade means in a position of maximum blower output up to a predetermined rotational speed including slide mean axially guided within said hub means and provided with cam-track means, follower means at said crankpin means engaging said cam-track means, and prestressed spring means within said slide means and operable in such a manner that the air pressure automatically adjusts the blade means to a lesser output as the rotational speed thereof exceeds said predetermined speed,

and second means for controlling the adjustment of said blade means in dependence on the temperature of the cooling air including thermostat means within said slide means and acted upon by the cooling air, said spring means engaging, on the one hand, directly with said slide means and seeking to hold the same against said fixed abutment means and being supported, on the other, against said thermostat means so that said thermostat means selectively increases or decreases the prestress of said spring means, and further means for axially adjustably supporting said thermostat means within said hub means,

said slide means being constructed as hollow body provided with a bottom and being open in the direction opposite the direction of flow of the cooling air, said thermostat means being movably arranged in the axial direction within said hollow body, and cover means provided with cooling air inlet bore means for closing the hollow space of said slide means.

4. An adjusting mechanism for automatically adjusting 10 thermostat means selectively increases or decreases the prestress of said spring means, and air discharge apertures being provided in the bottom of the slide means and in the hub means. 6. An adjusting mechanism for automatically adjusting the blades of a blower which are pivotally arranged in the the blades of a blower which are pivotally arranged in the hub portion of the blower, especially for internal cornbustion engines in motor vehicles, comprising:

hub portion of the blower, especially for internal combustion engines in motor vehicles, comprising:

blower hub means having fixed abutment means,

a plurality of blade means including pivot pin means rotatably supported within said hub means and crank pin means,

said blade means being of asymmetrical construction with respect to the longitudinal axes thereof,

first means normally holding said blade means in a position of maximum blower output up to a predetermined rotational speed including slide means axially guided within said hub means and provided with cam-track means, follower means at said crankpin means engaging said cam-track means, and prest-ressed spring means within said slide means and operable in such a manner that the air pressure automatically adjusts the blade means to a lesser output as the rotational speed thereof exceeds said predetermined speed,

and second means for controlling the adjustment of said blade means in dependence on the temperature of the cooling air including thermostat means Within said slide means and acted upon by the cooling air, said spring means engaging, on the one hand, directly with said slide means and seeking to hold the same against said fixed abutment means and being supported, on the other, against said thermostat means so that said thermostat means selectively increases or decreases the prestress of said spring means,

said slide means being constructed as hollow body provided with a bottom and being open in the direction opposite the direction of fiow of the cooling air, said thermostat means being movably arranged in the axial direction within said hollow body, and cover means provided with cooling air inlet bore means for closing the hollow space of said slide means,

said thermostat means being provided with an abutment disk, and said spring means, on the one hand, resting against said abutment disk and, on the other, pressing against the bottom of the hollow body whose outer surface abuts against the fixed abutment means.

5. An adjustment mechanism for automatically adjusting the blades of a blower which are pivotally arranged in the hub portion of the blower, especially for internal combustion engines in motor vehicles, comprising:

blower hub means having fixed abutment means,

a plurality of blade means including pivot pin means rotatably supported Within said hub means and crank pin means,

said blade means being of asymmetrical construction with respect to the longitudinal axes thereof,

first means normally holding said blade means in a position of maximum blower output up to a predetermined rotational speed including slide means axially guided within said hub means and provided with camtrack means, follower means at said crankpin means engaging said cam-track means, and prestressed spring means within said slide means and operable in such a manner that the air pressure automatically adjusts blower hub means having fixed abutment means,

a plurality of blade means including pivot pin means rotatably supported within said hub means and crank pin means,

said blade means being of asymmetrical construction with respect to the longitudinal axes thereof,

first means normally holding said blade means in a position of maximum blower output up to a predetermined rotational speed including slide means axially guided within said hub means and provided with cam-track means, follower means at said crankpin means engaging said cam-track means, and prestressed spring means within said slide means and operable in such a manner that the air pressure automatically adjusts the blade means to a lesser output as the rotational speed thereof exceeds said predetermined speed,

and second means for controlling the adjustment of said blade means, in dependence on the temperature of the cooling air including thermostat means within said slide means and acted upon by the cooling air, said spring means engaging, on the one hand, directly with said slide means and seeking to hold the same against said fixed abutment means and being supported, on the other against said thermostat means so that said thermostat means selectively increases or decreases the prestress of said spring means,

said slide means being constructed as hollow body provided with a bottom and being open in the direction opposite the direction of flow of the cooling air, said thermostat means being movably arranged in the axial direction within said hollow body, and cover means provided with cooling air inlet bore means for closing the hollow space of said slide means,

said thermostat means being provided with an abutment disk, and said spring means, on the one hand, resting against said abutment disk and, on the other, pressing against the bottom of the hollow body whose outer surface abuts against the fixed abutment means,

and air discharge apertures being provided in the bottom of the slide means and in the hub means.

7. An adjusting mechanism for automatically adjusting the blades of a blower which are pivotally arranged in the hub portion of the blower, especially for internal combustion engines in motor vehicles, comprising:

blower hub means having fixed abutment means,

a plurality of blade means including pivot pin means rotatably supported within said hub means and crank pin means,

said blade means being of asymmetrical construction with respect to the longitudinal axes thereof,

first means normally holding said blade means in a position of maximum blower output up to a predetermined rotational speed including slide means axially guided within said hub means and provided with cam-track means, follower means at said crankpin means engaging said cam-track means, and prestressed spring means within said slide means and operable in such a 7 manner that the air pressure automatically adjusts the blade means to a lesser output as the rotational speed thereof exceeds said predetermined speed,

and second means for controlling the adjustment of said blade means in dependence on the temperature of the cooling air, said spring means engaging, on the one hand, directly with said slide means and seeking to hold the same against said fixed abutment means and being supported, on the other, against said thermostat means so that said thermostat means selectively increases or decreases the prestress of said spring means, and further means for axially adjustably supporting said thermostat means within said hub means,

said slide means being constructed as hollow body provided with a bottom and being open in the direction opposite the direction of flow of the cooling air, said thermostat means being movably arranged in the axial direction within said hollow body, and cover means provided with cooling air inlet bore means for closing the hollow space of said slide means,

said further means being formed by a threaded stem portion threadably and adjustably received in a threaded part of said cover means,

said thermostat means being provided with an abutment disk and said spring means, on the one hand, resting against said abutment disk and, on the other, pressing against the bottom of the hollow body whose outer surface abuts against the fixed abutment means,

and air discharge apertures being provided in the bottom of the slide means and in the hub means.

8. A cooling blower especially for internal combustion engines in motor vehicles, comprising: a hub portion rotationally mounted; a plurality of blower blades; means for mounting each of said blades within said hub portion for rotation about acorresponding generally radially extending axis between a position of maximum blower output and a position of minimum blower output; each of said blades being of asymmetrical construction with respect to the axis thereof; a single spring means for normally jointly resiliently holding all of said blades in the rotational position of maximum blower output up to a predetermined rotational speed and for jointly automatically adjusting the pitch of all of said blades by resiliently allowing said blades to rotate toward the position of minimum blower output in response to the torque produced by the air pressure acting upon the asymmetrical blades as the rotational speeds of said hub portion exceeds said predetermined speed; and a single temperature responsive transducer means acting in series through said spring means to preload said spring means for jointly controlling the ad justment of said blades in dependence on the temperature of the cooling air that is being moved by said cooling blower by preloading said spring means in a direct relationship with the temperature of the cooling air to adjust said predetermined rotational speed in response to cooling air temperature changes.

9. The device of claim 8 including means for manually adjusting the preloading of said spring means to thereby adjust the value of said predetermined rotational speed.

10. The device according to claim 9 wherein said hub portion comprises a shaft, a cup portion rigidly attached to said shaft and opening in the axial direction opposite to the direction of cooling air flow; said spring means consisting of a single coil spring axially aligned within said cup shape portion.

- 11. The device of claim 10, including a cover plate substantialy closing the open end of said cup portion; said temperature responsive transducer means consisting of a single thermos-tat having one axial end abutting said cover plate; said thermostat having abutment means for axially moving relative to said one end in response to temperature variation; said abutment means engaging one axial end of said spring means; and the other axial end of said spring means abutting against the bottom of said cup portion,

12. The device of claim 11, wherein said cover plate includes said manual adjusting means, and said manual adjusting means consists of a substantially centrally located threaded hole in said cover plate and a screw mounted for axial adjustment in said threaded hole.

13. The device of claim 12, including a plurality of axially extending apertures in said cover plate to allow cooling fluid to enter said cup portions; said cup portion having a forward end that is provided with said cover plate and a rearward end provided with said shaft and the bottom of said cup portion; said rearward end of said cup portion having a plurality of rearwardly and radially outwardly extending air conduits for conducting fluid fro-m the rearward interior of said cup portion to the exterior of said cup portion by centrifugal force and by the circulation of air entering said apertures in said cover plate to provide a flow of cooling fluid through the interior of said cup portion.-

14. The device of claim 13, wherein said means for rotationally mounting each of said blades consists of a pivot pin rigidly attached to the radially innermost portion of each of said blades; the walls of said cup portion having a plurality of symmetrically spaced radially extending bearing bores corresponding in number to each of said pivot pins and extending from the exterior of said cup portion to the interior of said cup portion; each of said pivot pins being rotationally mounted in a corresponding one of said bores; a plurality of generally axially extending crank arms, each rigidly attached to a corresponding pivot pin; a generally tubular slide member mounted for axial sliding movement within said cup portion; each of said arms having an inwardly extending crank pin eccentrically located with respect to the corresponding pivot pin; said slide member having cam means engaging each of said crank pins for rotating said blades about the axis of their corresponding pivot pins upon axial sliding movement of said slide member; said slide member having a rearward abutment; said slide member abutment being disposed between said spring means and the bottom of said cup portion so that said spring means resiliently oposes any axial sliding movement of said slide member.

15. The device of claim 8, wherein said hub portion comprises a shaft, a cup portion rigidly attached to said shaft and opening in the axial direction opposite to the direction of cooling air flow; said spring means consisting of a single coil spring axially aligned within said cup shaped portion.

16. The device of claim 15, including a cover plate substantially closing the open end of said cup portion; said temperature responsive transducer means consisting of a single thermostat having one axial end abutting said cover plate; said thermostat having abutment means for axially moving relative to said one end in response to temperature variation; said abutment means engaging one axial end of said spring means; and the other axial end of said spring means abutting against the bottom of said cup portion.

17. The device of claim 16, including a plurality of axially extending apertures in said cover plate to allow cooling fluid to enter said cup portions; said cup portion having a forward end that is provided with said cover plate and a rearward end provided with said shaft and the bottom of said cup portion; said rearward end of said cup portion having a plurality of rearwardly and radially outward extending air conduits for conducting fluid from the rearward interior of said cup portion to the exterior of said cup portion by centrifugal force and by the circulation of air entering said apertures in said cover plate to provide a flow of cooling fluid through the interior of said cup portion.

18. The device of claim 17, wherein said means for rotationaly mounting each of said blades consists of a pivot pin rigidly attached to the radially innermost portion of each of said blades; the walls of said cup portion having a plurality of symmetrically spaced radially extending bearing bores corresponding in number to each of said pivot pins and extending from the exterior of said cup portion to the interior of said cup portion; each of said pivot pins being rotationally mounted in a corresponding one of said bores; a plurality of generally axially extending crank arms, each rigidly attached to a corresponding pivot pin; a generally tubular slide member mounted for axial sliding movement within said cup portion; each of said arms having an inwardly extending crank pin eccentrically located with respect to the corresponding pivot pin; said slide member having cam means engaging each of said crank pins for rotating said blades about the axis of their corresponding pivot pins upon axial sliding movement of said slide member; said slide member having a rearward abutment; said slide member abutment being disposed between said spring means and the bottom of said cup portion so that said spring means resiliently opposes any axial sliding movement of said slide member.

19. The device of claim 8, wherein said hub portion comprises a shaft and a cup portion drivingly secured to said shaft, said means for rotationally mounting each of said blades consists of a pivot pin rigidly attached to the radially innermost portion of each of said blades; the walls of said cup portion having a plurality of symmetrically spaced radialy extending bearing bores corresponding in number to each of said pivot pins and extending from the exterior of said cup portion to the interior of said cup portion; each of said pivot pins being rotationally mounted in a corresponding one of said bores; a plurality of generally axially extending crank arms, each rigidly attached to a corresponding pivot pin; a generally tubular slide member mounted for axial sliding movement within said cup portion; each of said arms having an inwardly extending crank pin eccentricaly located with respect to the corresponding pivot pin; said slide member having cam means engaging each of said crank pins for rotating said blades about the axis of their corresponding pivot pins upon axial sliding movement of said slide member; said slide member having a rearward abutment; said slide member abutment being disposed between said spring means and the bottom of said cup portion so that said spring means resiliently opposes any axial sliding movement of said slide member.

20. The device of claim 19, including a cover plate substantially closing the open end of said cup portion; said temperature responsive transducer means consisting of a single thermostat having one axial end abutting said cover plate; said thermostat having abutment means for axially moving relative to said one end in response to temperature variation; said abutment means engaging one axial end of said spring means; and the other axial end of said spring means abutting against the bottom of said cup portion.

21. The device of claim 20, including a plurality of axially extending apertures in said cover plate to allow cooling fluid to enter said cup portions; said cup portion having a forward end that is provided with said cover plate and a rearward end provided with said shaft and the bottom of said cup portion; said rearward end of said cup portion having a plurality of rearwardly and radially outwardly extending air conduits for conducting fluid from the rearward interior of said cup portion to the exterior of said cup portion by centrifugal force and by the circulation of air entering sai-d apertures in said cover plate to provide a flow of cooling fluid through the interior of said cup portion.

References Cited UNITED STATES PATENTS 1,820,742 8/1931 Hewitt -1 60.51 1,970,847 8/1934 Gibbs 170160.S1 1,978,788 10/1934 Furgason 170160.13 2,354,948 8/1944 Dewey 170160.13 3,220,484 11/1965 Elmer 170-160.53

ROBERT M. WALKER, Primary Examiner.

LAURENCE V. EFNER, Examiner. 

1. AN ADJUSTING MECHANISM FOR AUTOMATICALLY ADJUSTING THE BLADES OF A BLOWER WHICH ARE PIVOTALLY ARRANGED IN THE HUB PORTION OF THE BLOWER, ESPECIALLY FOR INTERNAL COMBUSTION ENGINES IN MOTOR VEHICLES, COMPRISING: BLOWER HUB MEANS HAVING FIXED ABUTMENT MEANS, A PLURALITY OF BLADE MEANS INCLUDING PIVOT PIN MEANS ROTATABLY SUPPORTED WITHIN SAID HUB MEANS AND CRANK PIN MEANS; SAID BLADE MEANS BEING OF ASYMMETRICAL CONSTRUCTION WITH RESPECT TO THE LONGITUDINAL AXES THERROF, FIRST MEANS NORMALLY HOLDING SAID BLADE MEANS IN A POSITION OF MAXIMUM BLOWER OUTPUT UP TO A PREDETERMINED ROTATIONAL SPEED INCLUDING SLIDE MEANS AXIALLY GUIDED WITHIN SAID HUB MEANS AND PROVIDED WITH CAM-TRACK MEANS, FOLLOWER MEANS AT SAID CRANKPIN MEANS ENGAGING SAID CAM-TRACK MEANS, AND PRESTRESSED SPRING MEANS WITHIN SAID SLIDE MEANS AND OPERABLE IN SUCH A MANNER THAT THE AIR PRESSURE AUTOMATICALLY ADJUSTS THE BLADE MEANS TO A LESSER OUTPUT AS THE ROTATIONAL SPEED THEREOF EXCEEDS SAID PREDETERMINED SPEED, 